The proposed study is an extension of the current project that was designed to study family and peer influences in the acquisition and maintenance of drug use and abuse within a 7-year age-cohort-sequential design. The focal subjects were ages 11-15 during the first assessment and aged 17-21 during the final one. In this application, we propose to follow up our sample for four years from ages 19-23 until 22-26. This would provide data on a crucial transition period of young adulthood that has had very little examination. The broad array of variables included in our previous data collection efforts on these adolescents, their parents, siblings, and peers provide a unique opportunity to identify predictors of use and abuse in the post-secondary-school period. Overall, we will be able to examine the period from ages 11 to 26 and combine data on initiation, cessation, maintenance, and consequences of substance use and abuse. Our sample of 522 young adults will be administered annual questionnaires and a brief standardized clinical interview (DIS) to identify substance use or dependence according to DSM- IIIR criteria (APA, 1987). Parents and friends will complete similar questionnaires. At T8 and T11, subjects will participate in two problem solving interactions (PSIs) with a spouse/partner, cohabiter, or someone they have identified as their best friend. Questionnaires will include an assessment of substance use, risk factors and consequences of substance use and abuse, as well as detailed information regarding role transitions and satisfaction with roles. Friend questionnaires will assess their own substance use, and behavior and attitude toward use, the target's use, and measures assessing their relationship with the target. Parents will provide data on their own use, perception of their child's use and behavior and attitude toward it, degree of contact, and variables assessing their relationship and cohesion within the family of origin. With the permission of the subject, transcripts, if relevant, and information regarding employment status, marriage, births, DWI, and arrest records will be obtained from official sources (e.g. court records, social security administration), from the employer regarding job performance. The analytic procedures we have begun to use and plan to continue to use are state-of-the-art statistical techniques precisely designed for the complexities of longitudinal designs. Data analysis techniques will include state-of-the-art procedures for longitudinal studies including simple descriptive, event history methods, structural equation modeling, latent growth curve analyses, generalized estimating equations, and regression techniques.